A Gallup analysis of three months of tracking polls published Friday found that married voters overwhelmingly favor Republican nominee Mitt Romney, 54 percent to 39 percent. There's an even bigger gap on the other side among single voters — they prefer President Barack Obama 56 percent to 35 percent.

What makes the marriage gap different than the gender gap is that it holds up across different demographics. Even highly religious unmarried voters prefer Obama by 6 points. Romney, on the other hand, scores much better with married voters in demographics where he usually struggles mightily — among non-white voters and non-religious voters, for example.

Gallup's Andrew Dugan writes that the marriage gap is a significant factor in the election:

The 2012 election is often framed in the competing demographics of the two rival bases: old vs. young, racial/ethnic minority vs. whites, and the rich vs. the poor. This analysis offers one more layer to this segmentation -- the married as opposed those who are not. While the candidates have framed this presidential contest as a battle among conflicting ideologies, it increasingly looks to be a matter of differing demographics as well.